Ne no Kuni-ke

One day, after being pushed by a colleague at work and hovering between life and death, Inukai Masayoshi arrives at a strange, enormous mansion called Ne no Kuni. He is about to be eliminated by a clan whose job it is to hunt aggregates of human impurity known as "rats" as they see him as the source of rats,
but he is saved by a young man named Haishiro, one of the candidates to become head of Ne no Kuni. Haishiro offers to help Masayoshi, who is about to be disposed of due to a certain clan "rule"...

(Source: Kadokawa, translated)